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Questions and Answers
What is the primary purpose of exocytosis?
What is the primary purpose of exocytosis?
- To remove unwanted molecules from the cell
- To secrete substances out of the cell (correct)
- To package proteins within the cell
- To move substances into the cell
Which of the following is NOT a type of endocytosis?
Which of the following is NOT a type of endocytosis?
- Phagocytosis
- Receptor-mediated endocytosis
- Pinocytosis
- Exocytosis (correct)
What is the primary function of the Golgi apparatus in the protein packaging process?
What is the primary function of the Golgi apparatus in the protein packaging process?
- To fuse secretory vesicles with the cell membrane
- To add post-translational modifications to proteins (correct)
- To translate proteins on ribosomes
- To insert membrane proteins into the cell membrane
Which of the following is NOT a post-translational modification that occurs in the endoplasmic reticulum (ER)?
Which of the following is NOT a post-translational modification that occurs in the endoplasmic reticulum (ER)?
What is the primary purpose of receptor-mediated endocytosis?
What is the primary purpose of receptor-mediated endocytosis?
What is the primary difference between exocytosis and endocytosis?
What is the primary difference between exocytosis and endocytosis?
What is the primary function of phagocytosis?
What is the primary function of phagocytosis?
Which type of cells are known for releasing histamine?
Which type of cells are known for releasing histamine?
What is the main function of receptor-mediated endocytosis?
What is the main function of receptor-mediated endocytosis?
Which drug is commonly used to treat epilepsy by reducing neurotransmitter release?
Which drug is commonly used to treat epilepsy by reducing neurotransmitter release?
What is the distinctive feature of constitutive secretory pathways?
What is the distinctive feature of constitutive secretory pathways?
Where do vesicle pools form in relation to synaptic zones?
Where do vesicle pools form in relation to synaptic zones?
What is the main function of phagocytosis?
What is the main function of phagocytosis?
Which process involves the fusion of an endocytosed vesicle with an 'early endosome'?
Which process involves the fusion of an endocytosed vesicle with an 'early endosome'?
What are early endosomes characterized by?
What are early endosomes characterized by?
Which disease involves the accumulation of LDL particles in the blood due to impaired endocytosis?
Which disease involves the accumulation of LDL particles in the blood due to impaired endocytosis?
In which process are amino acids, cholesterol, and fatty acids released by breaking down cargo?
In which process are amino acids, cholesterol, and fatty acids released by breaking down cargo?
What specific event triggers pinocytosis?
What specific event triggers pinocytosis?
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Study Notes
Exocytosis and Endocytosis
- Exocytosis uses energy (ATP) and involves the movement of substances OUT of the cell
- Exocytosis involves insertion of membrane proteins, secretion of substances (e.g. insulin, neurotransmitters), and removal of unwanted molecules
Protein Packaging
- Protein packaging occurs in the endoplasmic reticulum (ER) and Golgi apparatus
- Post-translational modifications in the ER include:
- Folding
- Assembly into multi-subunit complexes (quaternary structures)
- Disulfide bond formation
- Glycosylation (addition of sugars)
- Membrane proteins are added to the membrane as soon as they are translated
- Proteins are sorted and modified in the Golgi apparatus before being packaged into secretory vesicles
Exocytosis Pathways
- Constitutive secretory pathways: e.g. secretion of proteins and elements of the extracellular matrix
- Regulated secretory pathways: e.g. neurotransmitter release
- Exocytosis machinery involves membrane fusion and insertion of membrane proteins
- Secretory cells examples include mast cells, beta-cells of the pancreas, and goblet cells
Endocytosis
- Endocytosis is the movement of substances INTO the cell
- Types of endocytosis:
- Phagocytosis: large molecules
- Pinocytosis: small molecules
- Receptor-mediated endocytosis: specific molecules
- Endocytosis involves fusion with lysosomes for protein degradation
Pinocytosis and Phagocytosis
- Pinocytosis: "cell drinking", non-specific, maintains plasma membrane size
- Phagocytosis: receptor-mediated endocytosis of large molecules
Endocytotic Pathway
- Endocytosed vesicle first encounters an early endosome with a low pH
- Cargo is either returned to the membrane or transferred to a late endosome, which fuses with a lysosome
- Lysosome contains enzymes to break down cargo into constituent parts
Diseases Related to Endocytosis
- Atherosclerosis: genetic disorders can affect LDL particle uptake, leading to atherosclerotic plaques
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